This invention relates generally to monitoring the operation of a machine. In particular this invention relates to the automatic detection of extreme loads on driven members whether machine slides or spindles during the execution of a machine cycle of operation.
Historically, where the object of machine operation monitoring is operation control, forces or torques are monitored during program periods when work is expected to be performed on a workpiece. It is well-known for example to monitor torque during drilling operations to control feed rate and prevent tool breakage. Likewise, it is well-known to monitor force during grinding operations to control feed rate to produce accurate finished workpieces. Further, where the primary object of monitoring is the detection of worn or broken tools, it is known to detect peak power during a machine cycle and compare changes in peak power from one machine cycle to another against a predetermined limit. When the change in power exceeds a limit, an error or alarm is produced indicating an excessively worn or broken tool. It is known to record a profile of tool wear occurring over the execution of a plurality of machine cycles of operation and to use this profile to produce limits for detecting excessively worn or broken tools during monitored executions of the machine cycle. It is also known to store a measured load level in correspondence to the positioning of a selected machine slide or slides to a predetermined location. Tool wear or breakage is detected during subsequent executions of the machine cycle of operation by comparing measured load levels at the same selected position against the recorded value. These known monitors are all practically limited in applicability to loads detected during the performance of work on a workpiece. Further, these known monitors are intended to compare a measured force typically a gross force of a single driven machine member against a recorded value using a dedicated algorithm for determining the magnitude of the acceptable measured load.
It is, therefore, one object of this invention to provide a machine operation monitor for detecting load extremes occurring during a cycle of operation irrespective of the programmed activity at the moment of occurrence.
It is a further object of the present invention to provide a machine operation monitor for detecting extreme loads during a cycle of operation at moments when the programmed activity does not involve contact between a workpiece and tool.
It is a still further object of the present invention to provide a machine operation monitor for detecting extreme loads occurring during a cycle of operation from any of a plurality of machine member driving means.
It is a still further object of the present invention to provide a machine operation monitor for detecting extreme loads occurring during a cycle of operation which includes means for computing load limit values corresponding to machine cycle activity occurring at periodic intervals.
It is a still further object of the present invention to provide a machine operation monitor for detecting extreme loads occurring during a cycle of operation which includes means for computing load limit values according to a single algorithm based on net load applicable to loads measured at any and all of the machine member driving means.
Other objects and advantages of the present invention will become apparent from the following description.